Flexible printed electronics represent an emerging technology with potentially broad impact on everyday life. Printed devices such as environmental, physical, and biological sensors, logic circuits, radio-frequency transmitters, and display elements can enable a variety of applications in portable electronics, cybersecurity, biomedical diagnostics, and the Internet of Things. A cornerstone of this vision is the ability to integrate high-performance electronically functional materials in a low-cost, high-throughput, versatile manufacturing platform. Solution-phase printing methods such as inkjet, gravure, flexographic, and screen printing are well-suited for this purpose, offering high resolution patterning of liquid inks in a scalable manner. The development of inks based on electronic materials is therefore critical to progress in this field. Conductive nanomaterials have attracted significant interest in this regard, offering excellent electronic properties and compatibility with liquid-phase processing. In particular, recent efforts have focused on the application of graphene inks in flexible printed electronics, due to graphene's desirable combination of electrical and thermal conductivity, mechanical flexibility, chemical and thermal stability, and earth abundance.
The unique properties of graphene establish it as a promising alternative to traditional printed conductors, such as metallic nanoparticles and conductive polymers. Thus far, graphene inks have been demonstrated for a range of applications including flexible interconnects, transistor channels and electrodes, transparent conductors, and supercapacitors. Although initial work in this field focused on graphene oxide and its chemical derivatives, recent research has demonstrated dispersion and patterning strategies for pristine, non-oxidized graphene for high-performance applications. Despite these important advances, graphene inks that concurrently offer high electrical conductivity, strong substrate adhesion, and robust environmental stability have not been previously demonstrated.